Effect of Distal Core Flattening on 304 Stainless Steel Guide Wires

Abbott Vascular produces a variety of medical guide wires to accommodate a wide array of minimally invasive medical procedures. Certain types of these wires have the distal core flattened to improve specific properties such as flexibility and steerability. However, it is unknown how this affects the other mechanical properties of the wire. Abbott Vascular provided two types of wire to test the effects of distal core flattening on the mechanical performance of the wires. One group of wires was made from 304 single spring stainless steel with no flattening performed. The other group of wires was made from 304 triple spring stainless steel, which are cold worked to a greater extent than the single spring wires. Additionally, a 10-centimeter section of the triple spring wires are flattened for testing. Mechanical performance was tested through tensile and microhardness testing. Scanning electron microscopy (SEM) was also performed to observe the fracture surface of the wire. Tensile tests resulted in no discernable difference in ultimate tensile strength between the two wires but there was a noticeable increase to elongation to break for the triple spring samples. Single spring wires averaged lower Vickers hardness values than triple spring wires, but also had less variance in hardness along the length of the wire compared to triple spring wires. SEM imaging indicated neither pure brittle nor pure ductile fracture occurred at the fracture surface of the wires